Civil Twilight distances

Berneck1

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I was watching a video review by The Urban Prepper on the Thrunite Catapult V6. It was one of the more detailed reviews I've seen, and it had very practical details. (Not all detailed reviews are practical).

One detail that interested me was his use of Civil Twilight distances in rating a flashlight. I think we can all agree that distance ratings on flashlights are somewhat useless, and give no indication of what to expect in real world situations. If I'm understanding this correctly, this calculation gave the distance at which we would see an object in the evening as if it was right after the sun goes down. When things are still pretty light out. This to me is tremendously more practical than the bs distances all flashlights have printed on the box.

Are there other reviewers using this metric? And, don't you think this is something that should be standardized and used by all companies?

Btw, what I typically have done is quartered the distance rating on a flashlight to give me an idea of what to expect. For example, if the rating is 400m, I'll expect to see reasonably well out to 100m, in optimally dark conditions of course. And probably 50m if there are other light sources around. These distance ratings don't take into account other factors like other light sources that can obstruct your view, etc.

Just wondering what other people think on this....
 

wosser

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There are dozens of uncontrolled variables that affect perceived beam distance. Using Civil Twilight as a benchmark is a good idea in principle but it only ties down a small number of those variables, leaving all the rest unaffected.
Just listing all the variables would be an interesting task in itself (I'll try that later on).

I just wish that vendors would let customers have a test-drive for a weekend (or longer?). Perhaps some vendors do offer this, but I've never seen it.

Ultimately it is impossible to standardise a subjective quantity.
It is an interesting thought experiment to design an apparatus that would produce an objective measurement of "beam quality" from generic flashlights.
 
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Modernflame

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The full list of ANSI FL-1 standards on our flashlight packages is rubbish. In most cases, I also ignore the output and run time specs and do my own arithmetic. Don't even get me started on beam distance. Yes, one quarter of the distance is how far you'll actually be able to see, assuming the flashlight doesn't have to compete with fog or ambient light. Fortunately, my two favorite flashlight makers don't bs around with this.
 

MAD777

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I quarter the distance advertised LUX as well, if I think the company is honest, and reduce more for some less than honest companies.
In theory, the ANSI stardard distance for LUX puts 1/4 lumen/sq meter brightness on the target. Quartering that distance means 4 lumen/sq meter on the target. Still not much, but enough to tell there's a flashlight aimed at it.
But, the numbers are all relative, if properly measured. Probably the biggest variable is in the honesty of the company. LUX is what most of us want to know about a flashlight's throw. It tells us how bright the target will be lit at the center.

Candela (cd ) is a whole other ball game. The shape of the beam comes into play here. It's a measure of the brightness of an area defined as a circle with a radius from the center of the beam, to a point where the intensity is 50% of the center intensity. I think of it as the brightness of the hot spot, which can vary in size with every flashlight. This is unlike Lux, which is measured over 1 sq. meter, no matter the beam shape.

Here's a good article comparing lumen, lux and cd....
https://www.ledwatcher.com/light-measurements-explained/
 

flatline

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The full list of ANSI FL-1 standards on our flashlight packages is rubbish. In most cases, I also ignore the output and run time specs and do my own arithmetic. Don't even get me started on beam distance. Yes, one quarter of the distance is how far you'll actually be able to see, assuming the flashlight doesn't have to compete with fog or ambient light. Fortunately, my two favorite flashlight makers don't bs around with this.

I like how Streamlight puts the output vs time graph on the back of their packaging (and website). That, to me, is way more useful than the ANSI icons on the front.

I wish every brand did this.

--flatline
 

xxo

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Civil twilight is about 3.2 lux. To get the beam distance to 3.2 lux divide the cd by 3.2 and take the square root.

I find it pretty easy to use a rule of thumb for practical beam distance, I just take whatever they claim in Meters for the FL1 and change it to feet, which is the beam distance to about 2.75 lux.
 

Timothybil

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Civil twilight is about 3.2 lux. To get the beam distance to 3.2 lux divide the cd by 3.2 and take the square root.

I find it pretty easy to use a rule of thumb for practical beam distance, I just take whatever they claim in Meters for the FL1 and change it to feet, which is the beam distance to about 2.75 lux.
I have heard others use that method as well. For myself, I look at the F1 results as merely testing process somewhat like a Mil-Spec. The results are only useful in comparing with the same results for other lights, assuming everyone is doing the testing properly. Due to differences in color temp, size of hot spot, etc., applying those results to the real world is an exercise in futility.
 

bykfixer

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While being the sort who looks at an analog clock and sees it says it's about a quarter to nine (not 8:43), I just look at the cd number when available and get a sense of distance in a general fashion.

Example would be a 175 lumen number that says 5k cd vs 177 lumen one that says 12k cd. The first one in my minds eye says it's a spreader beam and the second says it's a thrower.

Regarding civil twighlight, my brain says more lumens is better. Say, a 177 lumen at 12k cd versus a 325 lumen at 12k cd, my brain equates the 325 being better. True or not? Got me. I just reach for a Maglite as they are good throwers.
 
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Berneck1

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While being the sort who looks at an analog clock and sees it says it's about a quarter to nine (not 8:43), I just look at the cd number when available and get a sense of distance in a general fashion.

Example would be a 175 lumen number that says 5k cd vs 177 lumen one that says 12k cd. The first one in my minds eye says it's a spreader beam and the second says it's a thrower.

Regarding civil twighlight, my brain says more lumens is better. Say, a 177 lumen at 12k cd versus a 325 lumen at 12k cd, my brain equates the 325 being better. True or not? Got me. I just reach for a Maglite as they are good throwers.

Yeah, recently I've been looking at candela more to get a sense on what type of beam it may have.
 

xxo

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While being the sort who looks at an analog clock and sees it says it's about a quarter to nine (not 8:43), I just look at the cd number when available and get a sense of distance in a general fashion.

Example would be a 175 lumen number that says 5k cd vs 177 lumen one that says 12k cd. The first one in my minds eye says it's a spreader beam and the second says it's a thrower.

Regarding civil twighlight, my brain says more lumens is better. Say, a 177 lumen at 12k cd versus a 325 lumen at 12k cd, my brain equates the 325 being better. True or not? Got me. I just reach for a Maglite as they are good throwers.




Most people are going to say light with higher lux is brighter than one with higher lumens, assuming that they are not too lopsided of a comparison. Back in the day cd, or before that candle power, was used to express brightness in flashlights which I think is a better indicator than lumens. Lumens are better for light bulbs, area lights and lanterns which are not intended to project a beam very far. IIRC Surefire was the first to advertise lumens for flashlights, probably because it was a measure that made their 2 CR123 lights more comparable to bigger Mags and Streamlights which had higher candlepower but similar lumen outputs.

I look at cd/beam distance along with beam patterns (size and intensity of the hot spot and spill) and not so much at lumens.
 

bykfixer

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Agreed xxo.

I suppose it was the generation 1 and 2 of the Pelican 2350 numbers to get a sense of perpective. Gen 1 was 100 lumens with iirc 11000+/- cd and the gen 2 is 175 with 9000+/- cd.

When I saw that I figured Pelican had changed the dynamics to end up with a wider hot spot and a nice Malkoff-esque spread from spot to spill.

When the gen 2 arrived it turns out they had indeed done just that.

Thing is, I could see objects at a distance better with the 100 lumen version. I don't always believe the brighter light will provide a better view of distant object, but at times it's the sideways lighting that causes the affect. The pencil beam (at least to my eyes) allows a better contrast of light at a distance and dark around that, which in turn allows my eyes to see distant objects without a whole bunch of 'candlepower'.
 

Berneck1

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Agreed xxo.

I suppose it was the generation 1 and 2 of the Pelican 2350 numbers to get a sense of perpective. Gen 1 was 100 lumens with iirc 11000+/- cd and the gen 2 is 175 with 9000+/- cd.

When I saw that I figured Pelican had changed the dynamics to end up with a wider hot spot and a nice Malkoff-esque spread from spot to spill.

When the gen 2 arrived it turns out they had indeed done just that.

Thing is, I could see objects at a distance better with the 100 lumen version. I don't always believe the brighter light will provide a better view of distant object, but at times it's the sideways lighting that causes the affect. The pencil beam (at least to my eyes) allows a better contrast of light at a distance and dark around that, which in turn allows my eyes to see distant objects without a whole bunch of 'candlepower'.

You bring up a good point about contrast. I've noticed as I have gotten older, I need a light with more throw to see better. Floodier lights tend to distract from what I'm trying to focus on, because my night vision has deteriorated. For that reason, the candela rating has become more important to me when making a determination on what to buy.
 
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